EVIDENCE-BASED ANSWER
The proportion of patients who are pain free or completely recovered after an acute episode of low back pain within 2 weeks to 6 months ranges from 21% to 90%, depending on the population studied and the method of measuring outcomes. The reported recurrence rates are also variable, from a low of 35% to a high of 75%, again depending on the length of follow-up and the study design. Grade of recommendation: C (on the basis of case-series, poor quality cohort studies, and case-control studies).
Evidence summary
It has been widely stated that 80% to 90% of attacks of acute low back pain resolve within approximately 6 weeks,1 though there is little evidence to support this claim. Although there are many studies and guidelines regarding treatment methods for low back pain, few studies evaluate the natural history of low back pain. One prospective series in a primary care setting found that 90% of patients were without pain 2 weeks after initial evaluation by their physician.2 This study had a 3-month follow-up period for 103 patients presenting with pain of less than 72 hours’ duration.
Another prospective study found that 94% of patients evaluated for a new episode of low back pain were no longer visiting their physician for treatment after 3 months. However, this was not an adequate measure of resolution of pain. Only 21% (39/188) were pain free at 3 months and only 25% (42/170) were pain free at 12 months.3 A larger study involved 1555 patients during a 6-month follow up after an episode of acute low back pain. The article reports a mean of 16 days to functional recovery, although only 69% of the patients considered themselves “completely recovered” at 6 months.4
Recurrences of low back pain are common. In one prospective cohort study of 443 patients with low back pain, 75% had a recurrence with a mean of 2 relapses in 1 year of follow-up, but only 228 patients completed the study.5 Another prospective study of 208 patients found that 35% to 44% of patients had recurrence of pain within 6 months of their first episode, and 50% to 59% had a recurrence in 22 months of follow-up.6 No studies identified findings or risk factors associated with higher recurrence rates.
Recommendations from others
The Agency for Healthcare Research and Quality (www.ahcpr.gov) section on health outcomes (see http://www.ahcpr.gov/research/jan99/ra6.htm) states, “recent studies suggest that once experienced, low back pain becomes a part of life for almost half of those affected, and for many, it is intermittently disabling. Repeated visits and procedures do not appear to improve patients’ long-term well-being, but they clearly account for substantial health care costs. Finally, back pain prognosis does not differ based on the type of provider initially seen or the level of practitioner confidence.” This site offers several nice summaries of studies on low back pain.
Read the clinical commentary by Anne Fitzsimmons, MD, at www.fpin.org.